Fairy rings are a feared but common turf malady caused by growth of mushroom forming fungus. The growth occurs most usually in areas where there are high concentrations of lignin. Sawdust, buried logs or timbers, decorative bark or wood chips that have been tilled under, will often eventually encourage fungal growth that can result in fairy rings.
Many extension agents, horticulturists, plant treatment specialists and others recommend treatment of fairy rings to include excision or removal of effected soil to a depth of 12", followed by replacement with fresh top soil and re-seeding. Others suggest rigorous tillage to similar depths, followed by heavy irrigation and fertilizer treatment. Still others suggest chemical treatment, using flutolanil (a benzanilide fungicide) or methyl bromide. Complete soil sterilization may result from herbicidal treatment and remediation of the soil may not be possible for a period of years.
Part of the difficulty experienced with fairy rings is that the "cobwebby" root structure of the fungus, called mycelium, saps the soil of nutrients and blocks effective passage of water to other plant roots. The surrounding turf will thus die away.
From the above, it may be understood that there has been a long-felt, but substantially unfulfilled, need for an effective treatment of fairy rings.
It has been known, as suggested in U.S. Pat. No. 5,330,964, that bicarbonate of soda can be used as a herbicide. The '964 patent suggests placement of a heavy layer (between 1/8 and 1/4 inches) of soda on undesirable plants such as moss, poison ivy, clover, grasses and others. Such a heavy coating on the plants and surrounding soil will undoubtedly destroy the coated plants; but for practical purposes, the amount of material stated as necessary to cause a herbicidal action appears to be impractical, and regeneration of plant life in the treated areas is significantly delayed.
The specification in the '964 patent states that in tests where an initial coating of 1/8 inch of soda was applied, no new vegetation growth occurred in the treated area for a period of two years and that longevity of growth control is a function of the coating thickness. A statement is made that thinner coatings of less than 1/8 inch may be used for shorter periods of controlled new growth, but no reduced thickness is disclosed and results are admittedly speculative.
The '964 patent also discusses application of an aqueous solution of one part water to one part soda as an alternative to powder coating, though application rates are not disclosed apart from a general statement that the solution should be sprayed to an extent that the unspecified, unwanted vegetation is "soaked". No specific discussion is made in the patent regarding control of fairy rings or fungus.
U.S. Pat. No. 4,599,233 discloses a fungicide and fruit storage disease-preventing agent which includes sodium bicarbonate and a food emulsifier surfactant. Specific examples are listed, with various specific surfactants used to treat fungus growth on plants. The compound is thus used to treat growth of fungus on living or harvested plants as opposed to an herbicidal action on the plants themselves.
Neither of the above patents disclose a substantially exclusive treatment for fairy rings.
A coating as suggested in the '964 can be used to destroy vegetation, and therefore could be used to destroy fairy rings. However, the coating thicknesses suggested will result in destruction of adjacent coated vegetation and re-growth will be prevented for unacceptably long periods. Thus, the treatment disclosed in the '964 patent may be effective as a general herbicide, but would not be an attractive solution in areas where part of the plant growth is not to be destroyed, for example in turf where fairy rings occur in the midst of otherwise healthy, desirable vegetation.
No fairy ring treatment is specifically suggested in the '233 patent. Further, it is not likely that the disclosed fungicide treatment (which is used only to control fungus growth on plants) would destroy subsurface mycelium. No destruction of undesired fairy rings would likely result from use of the '233 fungicide.
Thus, a need remains for an effective treatment specific to the problem presented by fairy rings and the adverse effects produced by soil nutrient robbing mycelium found in the soil under fairy rings.